Influence of alkaline treatment on hemp fibers filled poly(lactic acid)

Sustainable composite materials can be produced by a combination of natural fibers and biodegradable polymers. In this study hemp fibers reinforced polylactic acid (PLA) has been produced by compounding extrusion. The morphology of hemp fibers has been chemically modified through alkaline treatment with the aim of obtaining better mechanical properties. This treatment is known to remove waxes and non-cellulosic surface components. Scanning Electron Microscopy (SEM), thermo gravimetric analysis (TGA) and tensile tests have been carried out to evaluate the mechanism of action of the alkaline treatment and the influence of this treatment on the fibers and composite properties. SEM evaluations and measurements have shown that the treatment improves the mechanical properties of the composite significantly. This result can be justified by the opening of the fibril clusters that produces a reduction of the average diameter of the fibers and a better dispersion within the polymer matrix.